Motorists are being urged to avoid part of Mitchell Freeway after a police incident forced the closure of northbound lanes in Perth’s northern suburbs.

Mitchell Freeway is closed between Hepburn and Whitfords avenues in Padbury, with major crash officers at the scene.

It is understood the incident involves an alleged hit-an-run of a pedestrian.

The 22-year-old man died at the scene.

Traffic is heavy on approach and drivers are being warned to take extra care when exiting via the Hepburn Avenue off-ramp.

Motorists are being urged to consider using the Warwick Road exit as an alternative route while the incident is cleared.

Drivers have been told to expect delays and plan ahead.

Elsewhere, a crash on Mitchell Freeway northbound at Warwick Road in Duncraig blocked the left emergency lane, with traffic heavy on approach and drivers urged to proceed with caution.

On Kwinana Freeway southbound after Beeliar Drive in Atwell, debris is affecting the right lane, though traffic is flowing.

A separate crash on Kwinana Freeway northbound at South Street in Bateman has also been cleared but traffic remains slow.